This invention relates to electronic apparatus for producing music, and more particularly relates to such apparatus in which the characteristics of the notes are produced by digital circuitry.
In recent years, digital circuitry has been gaining favor for use in electronic musical instruments and synthesizers due to its high reliability, accuracy and cost effectiveness. Ideally, the digital circuitry should produce numbers representing a variety of different characteristics of each musical note, such as waveform, fundamental frequency, volume, decay envelope and attack envelope. However, the known techniques for designing such circuitry are so complex that they have not resulted in a commercially-feasible product. The failure of the industry to overcome these design complexities has been a major stumbling block to the development of an all-digital synthesizer. One of the principal design problems is that normal digital circuitry requires a long time to calculate the ultimate composite characteristics of a note--too long for purposes of a performing-type instrument which must instantaneously respond to the touch of a performer.
As a result of these difficulties, past electronic musical synthesizers and instruments have used a combination of analog and digital techniques. For example, the waveshape information may be produced in the form of digital numbers, but the volume information is produced by means of an analog signal which controls the amplitude of an output amplifier. Such an approach is a compromise to an all-digital system, which reduces reliability and introduces sources of error. In addition, individual control over each note is sharply reduced.
Accordingly it is an object of the present invention to provide an electronic musical instrument or synthesizer in which the characteristics of individual notes are generated and combined digitally.
It is another object of the present invention to provide an instrument or synthesizer of the foregoing type in which individual notes are synthesized by generating separate amplitude and waveshape characteristics.
Still another object of the present invention is to provide an instrument or synthesizer of the foregoing type in which each musical note is digitally-generated by producing numbers corresponding to the volume, attack-decay envelope, waveshape and fundamental frequency of the note.
Yet another object of the invention is to provide a synthesizer or instrument of the foregoing type in which the digital numbers are combined by converting one of the numbers to an analog signal and then multiplying the analog signal times one of the other digital numbers.
By employing the techniques described herein, an electronic musical instrument or synthesizer can be produced which is capable of digitally controlling the essential characteristics of two or more notes played simultaneously with sufficient speed to operate as a performing instrument on a real time basis.